100 
MUSEUM BULLETIN NO, 2. 
Utah, Wasatch Mountains. — The sedimentation in the different 
portions of the Wasatch mountains varies so greatly that the 
individual sections will be described in detail. The Bear 
River plateau or range, with the Blacksmith Fork, Utah, section 
upon its western flank and the Mill canyon, Idaho, section 
upon the east, is also to be included in the northward extension 
of the Wasatch mountains though it lies to the east of the 
Wasatch mountains proper and is separated from that range 
by a pronounced depression. 1 The Wasatch Canyon, Ogden 
Canyon, and Big Cottonwood Canyon sections occupy positions 
along the north-south line formed by the western escarpment 
of the Wasatch mountains. In the southern portion (Big Cotton- 
wood canyon) Olenellus occurs in siliceous shales at the top of the 
quartzitic ser'es (see below); 70 miles to the north (Wasatch 
canyon), and in the Bear River range immediately to the east 
(Blacksmith Fork and Mill canyon) conditions favouring 
the deposition of sandstone appear to have continued into the 
Middle Cambrian and the upper portion of the quartzitic series, 
here named the Brigham quartzite, is referable to the Middle 
Cambrian. 2 (See also the summary statement, pages 110-111). 
Utah, Wasatch Mountains, Big Cottonwood Canyon. —An 
unfossiliferous quartzite 1,000 to 1,500 feet thick, conformably 
overlain by arenaceous shales containing Olenellus, itself rests 
with angular unconformity upon an almost similarly metamor- 
phosed quartzite, slate, and conglomerate series approximately 
10,000 feet thick, the erosion surface being so uneven that in 
places the upper quartzite series even rests on a much older 
gneiss and schist series which has been referred to the Archsean. 3 
Here the weight of evidence would seem to be in favour of a 
Pre-Cambrian age for the quartzite, slate, and conglomerate 
series, and a Lower Cambrian age for the upper quartzite 
series. 
1 The classic reports on the geology of the Fortieth Parallel by King, Hague, 
and Emmons, with their accompanying atlas, still contain the only comprehensive 
description and delineation of the geology of the area included within this mountain 
system. 
2 Middle Cambrian fossils have been found in the Brigham quartzite in Mill 
canyon only (see p. 102), but there as well as throughout the area the quartzite series 
ia immediately overlain by beds similar both in lithology and faunal content, and 
the generalization would appear to be applicable. 
* Blackwelder: Bull. Geol. Soc. America, vol. 21, 1910, p. 523. 
